Unfortunately, though, adjustment does not work at all if there is a back-door path we cannot block because we don’t have the requisite data. Yet we can still use certain tricks even in this situation. I will tell you about one of my favorite methods next, called the front-door adjustment. Even though it was published more than twenty years ago, only a handful of researchers have taken advantage of this shortcut up Mount Intervention, and I am convinced that its full potential remains untapped.
